Roller Compacted Concrete Structural Design Methods – Review of International Practice

Authored by John Figueroa, Director, John Figueroa Consulting Pty Ltd
Endorsed by James Walker, Vice President, ASCP

Summary

Fatigue studies from the 1980s demonstrated that RCC’s strength and fatigue performance are comparable to, or even better than, those of conventional concrete pavements. Traditional concrete pavement design often relied on the concept of an "endurance limit," defined as the stress level below which fatigue failure is improbable. For conventional concrete, this limit is typically set at 45–50% of flexural strength, while the Portland Cement Association (PCA) adopted a slightly lower value of 40% for RCC based on recommendations by the Construction Technology Laboratories (CTL). Nevertheless, modern mechanistic-empirical design approaches have moved beyond the endurance limit, favouring probabilistic methods that integrate reliability and account for the proportion of slabs expected to crack by the end of their design life. Laboratory fatigue studies indicate that RCC generally exhibits slightly higher flexural strength and modulus of elasticity compared to conventional concrete with similar compressive strength. This report provides equations to quantify RCC's properties and fatigue performance.

For RCC thickness design, until the methodology in Chapter 9 of the Austroads Guide to Pavement Technology Part 2: Pavement Structural Design (AGPT02-24) is updated, it is recommended to continue using Austroads' load safety factors for designing RCC pavements in light and moderate traffic applications. Nevertheless, efforts should focus on adopting a more refined fatigue model to improve design accuracy and minimise unnecessary conservatism.

One commonly used program in the United States is StreetPave, which enhances the PCA methodology with a more advanced fatigue model. This model explicitly incorporates reliability considerations and accounts for the percentage of slabs expected to crack by the end of the design life. Additionally, StreetPave integrates updated laboratory and field performance data, providing a more realistic reflection of pavement conditions and eliminating the need for load safety factors.

Globally, the concrete pavement industry has adopted mechanistic-empirical design methods for RCC road pavements, reflecting trends in conventional concrete pavement design. These methods provide performance-based solutions that address traffic loads, environmental factors, and material properties, ensuring optimised pavement performance.

In Australia, RCC has been used intermittently since the early 1980s in road pavements, haul roads, hardstand areas, and container yards. Nevertheless, it has not gained widespread acceptance for highway pavements, with its primary applications remaining as a subbase or working platform for rapid pavement reconstruction at intersections. Its broader adoption has been constrained by limited local supply, lack of suitable paving equipment and the absence of comprehensive technical guidelines and specifications.

Despite these challenges, RCC remains a cost-effective and sustainable choice for many applications. Its ability to incorporate recycled materials and support rapid construction makes it particularly attractive for sustainable pavement solutions. Additionally, the use of high-density paving equipment with automated level control systems is expected to lessen reliance on steel rollers for compaction.

Recent advancements in materials and construction techniques, particularly in Europe and the U.S., are significantly improving RCC's surface characteristics. Innovations such as shrinkage-compensating admixtures, enhanced joint treatments, use of synthetic fibres, and advanced finishing techniques including troweling, brooming, and tining have enhanced RCC's surface durability and ride quality. These developments are positioning RCC as a competitive alternative to other pavement types, with its improved performance and surface characteristics paving the way for broader adoption in the future.